Gradometer



GRADOMETER Filed Jan. 7, 1928 ifs =1.

- 1 Ti kg I 6 rials/Emma Patented Feb. 21, 1933 UNITED STATES PATENT! OFFICE-1 JOSEPH ELBAIR, F CAMP: HILL, PENNSYLVANIA.

GRADOMETER I Application filed January 7, 1928; Serial No; 245,213.

My invention relates to gradometers and move'from end to end in the tube,-as it were performancemeters of the class comprising a variously tilted, to meet the requirements of curved, glass spirit-level carrying fluid and gravity. This is precisely what is accoma bubble therein and a scale therewith, and plished in my invention. And to achieve it,

5 which is adapted to be installed in a motor ELISBOOIICl principle-capillarity is taken advanvehicle to register the grade traversed by it, tage of. The container is so constructed that and to denote by the advancement and retracit hasa main, longitudinal canal, in cross tion of the bubble, due to the acceleration and sectional size, beyond the range of capillarity retardation of'the speed of the vehicle, its ofthe fluid it contains, and one or moreacperforming capacity. This capacity is alcessory canals, co-operating with it, each Ways directly. expressed in terms of the hill wlthln the range of capillarity. Fluid will climbing capacity of the motor or in terms notdrain'out between surfaces, by gravlty, of down hill holding capacity of the brakes. that-are within the bounds of capillarity, and The invention is also applicable to aero therefore no matter how' large the bubble planes to measure their longitudinal and may be in the main canal, the fluid connections transverse inclinations in flight and to indiunder'it'in the accessory canal is alwaysthe cate oftheir efiiciency by means of their same. The travel of the bubble is not iinaccelerating ability. peded, or blocked, by its size, and the object The primary object of the invention is to is ideally accomplished. provide a gradometer that is simple and prac- Cap1llarity for different fluids and for diftical, accurate and reliable, inexpensive and ferent containers is vastly different. The self-contained and at the same time is ornate. size of thecapillary canal and its material, Another object is to provide, at the same and-even the fluid, are by no means the onlytime and with the same device, means for factors. Temperature is one of the main measuring the acceleration and retardation factors that concerns this invention. The capacity ofthemotor-vehicle in which it is most practical size for the main canal is installed and by means of which the over-all about one sixteenth of an inch in diameter. efliciency of said vehicle can be ascertained. This is under all conditions above the'capil A form-upon which the results of these e1nlary range of any suitable fluid, which may pirical tests on the vehicle, when in prime be alcohol, carbon tetrachloride or benzine; condition, can be tabulated and retained in an It is best to keep the tube in size as near just accessible position for comparisonwith subabove the capillary limit as possible for then sequent tests to ascertain how near to, or the fluid COIltEllIlGCl in the spirit level Will be how far from,'the norm each test comes. the-minimum and the bubble will be" least This device is so constructed as to obviate fi' ct in Size due tocold and heat. The the common difficulties of bubblev adaptation, i t 0f the accessory canal, to maintain the under varying conditions, to the requirements p ary t rac i011, and'to prevent the bubof gravity and to provide the same facility l rom dipping down between its walls as for the bubble excursions, due to acceleral 'g is o ne thirty w d O an 9 tion and retardation of the vehicle in which inch. Its depth depends on the specific gravit is installed, so as to be the means by which ity of the fluid used. On its depth depends its power and resistance factors can be meas the extent of .the bubbles excursion for any ured. given power impulse. It is desirable to make If it were possible to have a very small the depthsuch that the bubble moves tothe glass-tube, say about one sixteenth of an point'on the scale of percent grade, of the inch bore as compared with the standard size gradometer, upon full acceleration to repreof: about three eighth of an inch, and if it sentthe hill-climbing capacity of the motor were possible to maintain the meniscus, or vehicle in which it is installed. This depth fluid connection, under the bubble in that for'alcohol is approximately one eighthv of 1 small tube then the bubble would be free to an inch; for carbon tetrachloride it is less.

When a depth of the accessory canal is found that allows the bubble to advance to the proper point upon acceleration, upon retardation by brakes it will also retract to the point on the scale to indicate restraining power.

In this construction the amount of fluid, in the entire tube, at a mean temperature, is about forty times the volume of the bubble, instead of three hundred times its size in the standard type. In the warmest weather the bubble is still large enough to be favorably visible, while in the coldest, cold weather it is still a fairly small globule not over three times the volume of that in the warmest weather. Ata mean temperature, when motoring is most general the bubble is at the most favorable size. At no time, whether in the hottest or coldest weather, can the bubble partake of, and react to, the jolts which produce the distracting tremors in the normal spirit-level and which render the pendulum useless for the purpose in a moving vehicle. The globule responds only to the demands of gravity, acceleration and retardation. t

It is essential that the fluid in the tube be non-freezable, and that its expansion and contraction to heat and cold be the minimum. Of the fluids tested for the purpose it is found that carbon tetrachloride is the most suitable because its specific gravity is several times that of alcohol, or of petrol. Its freezng point is much lower as also is its freezing contraction. Its viscosity is also less. It takes a certain, pale stain which gives the bubble, by contrast a mellow, mercuryli ke sheen which renders it very much more yislble, especially in the twilight when readings are normally difiicult.

When the excursion of the bubble, in the gradometer attached to a motor vehicle, is the measuring means for the power or the resistance applied to the vehicle to produce acceleration or retardation, thereof, its inevitable change of size due to varying temperatures must not be a varying factor in its amoimt of excursion for a given acceleration or retardation of the vehicle. In the common, spirit-level, and in the commercial gradometer where the common, curved spiritlevel is adopted, the lower the temperature the. larger the bubble, and inversely, the smaller the meniscus, or fluid connection under the bubble and by means of which the fluid is transferred from one end of the bubble to the other when itmakes a change of position. The speed and distance of the bubble excursion, due to a certain amount of acceleration, is related to the size of fluid connection under the bubble. But in this invention, no matter what the size of the. bubble, thefluid connection underit is always the same andthe amount and facility of its excursion,

for a given power or resistance application, to the speed of the vehicle in which it is installed, is always the same. Connected with a scale it is a most accurate and convenient means of measuring power and resistance.

Referring now to the drawing:

Figure I is a plan view of the gradometer.

Figure II isan elevational view of the preferred form of the spirit-level to be used in the gradometer.

Figure III is a side elevation of the case with the glass spirit-level installed.

Figure IV is a bottom view of what is shown in plan in Figure I and in elevation in Figure III.

Figures V, VI, VII and VIII show enlarged, cross-sectional Views (the sections being through the bubble VIIIVIII of Figure II) of various modifications of the preferred type (Figure VIII) that all fulfill the requirement of always maintaining the fluid connection under the bubble, no matter what its size, by means of capillarity.

1 is the formed-up case which carries the scale S and the percent, grade numbers N and which houses the curved, glass spirit level 2 to which it conforms and half em beds in a trough which terminates in hasps 6 to retain the half embedded tube in position. The scale and numbers on the case parallel the tube. The case is so curved and has such a velvety, non-glare texture, and the top is so flared that no matter where the source of light is or from what position the scale is read there is no obscurity or high lightto render difficult the reading of the instrument. The trough in the botom of the case is bottomless which permits the glass to be pushed up from below into position against the hasps and to be retained there by cars 5 adapted to be bent over for the purpose. The bottomless trough also permits the light to seep in from below through the glass bearing, the pale-tinted liquid giving it a glow, which by color contrast it imparts to the bubble, which otherwise, and normally, would have an evanescent haziness, substance and legibility and a mellow sheen and which makes it resemble a highly lighted globule of mercury.

The curved glass-tube, embodying the spirit-level 2, carries a trough 8, integral with it, which conforms to its curvature and communicates, throughout, with its main canal. In the forms of levels 2 and 2c, the accessory channels 3 and 30 are attained by casting them integrally with the tubes while in tubes 2a and 2?) they are accomplished by inserting a trough 3a and a half-round 36 each of which conforms to the tubes curvature and is sealed into position with the tube at its ends. All the bubbles, 0, 0a, 06 and O0, differ in cross-sectional shape because of different inserts or of the modification of the tubes carrying them. It is obvious that the structure of these tubes, or their inserts, may be modified in an indefinite number of ways and yet fulfill the essential requirements of the invention. These requirements are that the structure of the tube to be filled with liquid and a bubble, and constituting the spirit level, embraces a main channel that is beyond the range of its capillary-attraction for that fluid, and an accessory one (or ones), conforming to it and communicating, throughout, with it, but which is (or are) within its capillary-attraction range for the fluid, and which co-operate with said main channel in maintaining a fluid connection under the bubble therein, no matter What its variation in size may be.

The means of attaching my invention to a motor vehicle, is a bracket, or stud, 7, illustrated in Fig. III. The fixture is screwed, or clamped at a convenient place so that its pivoting eyelet 8, spanning the distance between the side-walls of case 1 and lining up with the holes 16, are engaged by a bolt by which they can be tightened rigidly to maintain the bubble 0 always at the zero point of the scale S when the vehicle stands on the level.

Having now described my invention, and disclosed it in terms of the principles embodying it, I claim:

1. In a gradometer a tube containing fluid to form a bubble said tube comprising a main channel in size beyond the virtual range of its capillarity for said fluid and an accessory canal; said channel and canal being substantially parallel and in open free communication substantially throughout their eflective course.

2. In a gradometer comprising a spirit level, a scale and means for installing it in a motor vehicle the combination of a tube containing fluid to form a bubble; said tube comprising a main channel in size beyond the vir tual range of its capillarity for said fluid and an accessory canal within the virtual range of that capillarity and communicating and cooperating with the main channel in such a way that said bubble always advances or retracts to the same degree to any given increment of power or resistance asserted on said vehicle and indicates on the scale substantially as described.

3. In a gradometer comprising a spirit level the combination of a tube and a narrow channel substantially parallel therewith and in open free communication with each other substantially throughout their effective course, substantially as described. 7 JOSEPH H. BAIR. 

